I need parenting advice...

I am so disappointed right now. We have an agreement with C that goes as follows: When we (the parents) or I (the Mom) aren't home, there will be no kids over.

Pretty simple, right?

Colin has no key, but he has the code to our garage. In order to get to our garage you need a neighbour to let you into the common space.

So today after lunch. he said he was gonna meet his buddies on the soccer field. Usually that's where they meet then they go to the grocery store and buy some bullshit, soda and candy and go to somebody's house to play = play video games or the like. They don't often come to our house because I don't like a silly and loud crowd messing up the place. Plus we don't have a playstation. 

If C wants to have kids over he needs to ask my permission beforehand. It's been like this forever.

So today I told him I needed to go back to work for another 2-3 hours. If for some reason he wanted to come home he needed come to the office instead. It's all within walking distance, and he has his bicycle. Sooooo... (can you tell where this is going..?)

Tamara

I went to work, I went to the post office, I picked up dinner, I come home. The door that connects our garage to the basement was wide open. Huh? I was pretty sure I closed it. The light in the basement was on. I was pretty sure I turned it off. I parked, got out, heard giggling and shrieking from the house. At least no ax murderer or other evil intruder, but DAMN, what part of "no kids" didn't he get?

Tamara

They (four of them) were just about to put on their shoes and leave when I came in. They immediately stopped giggling and stared at me. 

I said "HELLO? What's going on here?" One of them couldn't help himself and giggled some more. 

"I'm not sure if you're aware of the agreement we have with Colin, no visitors when we're not around?" 

Nobody said anything. 

"I'm not happy right now. I take it you were just about to leave?" 

They nodded, got dressed, yelled "Bye, Colin" and ran.

Tamara

C was pretty contrite. 

He apologized, but I could tell the thing he was sorry about the most was that he got caught. 

I calmly talked to him about trust and stuff and said our house wasn't a youth club. 

He apologized some more. I am still so disappointed. I can't even yell.

I get that he wants to be cool and invite his friends over, but frankly I am not impressed with them as a crowd. 

They spilled Coke (should I be happy it's the soft drink, not the drug?) and used our bathroom (there is a guest bathroom, but they used ours. It smelled badly, and the sink was a mess. I guess that's a good sign because at least the washed their hands?

And because they felt they had to leave immediately they didn't clean up the toys, but C did it without whining. He's smart that way. He asked "where is that new book you gave me the other day?" - "It's grounded for the time being." "Too bad, but I figured that much." 

He was also clever enough not to ask for the iPad. So he's in his room now, reading something.

Tamara

I don't even know what to do about it. Do I tell the husband, he's not going to be thrilled, but usually when I am this mad he supports his son. My goal is I want to be able to trust Colin. How do I show him there's consequences for messing up and still have him talk to me about doing something he shouldn't have?